Fluid and elastomer apparatus, i.e., hydraulic mountings, isolators, and dampers include a fluid which augments the isolation and/or damping characteristics that may be achieved within elastomer mountings alone. This augmentation may take the form of adding additional tuned damping or tuned inertial effects. Fluid mountings are generally described in LORD.RTM. Technical Article LL-2166 entitled "Understanding Hydraulic Mounts for Improved Vehicle Noise, Vibration and Ride Qualities" by W. C. Flower. Commonly assigned U.S. Pat. No. 4,811,919 to Jones describes an inertial-type fluid mounting which incorporates a volume compensator.
Other examples of elastomer and fluid apparatus may be found in commonly assigned U.S. Pat. Nos. 5,540,549 and 5,501,434 to McGuire, 5,413,320 to Herbst, 5,374,039 to Schmidt et al., 5,197,692 to Jones et al., and 5,127,607 to McGuire. Fluid isolators, which are a subset of general fluid apparatus, are, in essence, tunable passive devices which use a fluid mass to create inertial forces which are used in conjunction with spring or elastic forces to tune the isolator dynamic characteristics relative to the frequency of vibratory input.
U.S. Pat. No. 4,236,607 to Halwes describes a vibration isolator having a tuning mass including a liquid which generates amplified counter-inertial forces. Notably, Halwes suffers from the problem that it cannot adequately compensate for temperature differentials which cause expansion of the fluid therein. Further, it may be difficult to obtain enough fluid mass in the straight-through inertia track design as described in Halwes. Further, there is a lack of tuneability in Halwes. Furthermore, the pockets formed in elastomer to receive lugs 34 in Halwes may act as stress concentrators which may adversely effect rubber fatigue. Simply, it may be advantageous to have a larger surface area to reduce rubber stresses within the part. Optionally, it may be desirable to lower the length of the isolator.